Is Rett Syndrome Genetic?

What Causes Rett Syndrome?

Rett syndrome is caused by a mutation in the MECP2 gene, which is located on the X chromosome. This gene provides instructions for making a protein that is essential for normal brain development. The protein acts like a switch, helping to regulate the activity of other genes in the brain.

When the MECP2 gene is faulty, brain cells cannot communicate properly. This disruption affects the developing brain and leads to the loss of skills and functions typical of Rett syndrome. The severity of the condition can vary widely because the specific mutation, the location of the mutation, and the pattern of X-chromosome inactivation all influence how the disorder presents.

Is Rett Syndrome Inherited From Parents?

In about 99% of cases, Rett syndrome is not inherited. The mutation occurs spontaneously—often referred to as a *de novo* mutation—when the egg or sperm is forming, or in the early stages of embryonic development. The parents are healthy and do not carry the altered gene.

There is a rare exception. In less than 1% of cases, a parent may carry a mutation in the MECP2 gene without showing symptoms, a situation known as germline mosaicism. In these cases, the mutation is not present in the parent’s blood cells but exists in their egg or sperm cells. If a parent carries this hidden mutation, the risk of having another child with Rett syndrome increases slightly.

Why Does Rett Syndrome Mostly Affect Girls?

Because the MECP2 gene sits on the X chromosome, the condition follows a specific pattern related to sex. Girls have two X chromosomes (XX), while boys have one X and one Y chromosome (XY).

A girl with one mutated MECP2 gene and one normal copy will develop Rett syndrome. The normal copy provides some protection, which is why girls survive. A boy who inherits a mutated MECP2 gene has no second X chromosome to compensate. This usually results in severe encephalopathy and is often fatal before or shortly after birth. This is why Rett syndrome is overwhelmingly diagnosed in females.

What Are the Symptoms and Stages of Rett Syndrome?

Rett syndrome is a progressive neurological disorder. Symptoms typically appear after a period of normal development, usually between 6 and 18 months of age. The condition is often described in four stages.

Stage one (early onset): This stage begins between 6 and 18 months. The child may show subtle signs like reduced eye contact, decreased interest in toys, and slight delays in sitting or crawling.

Stage two (rapid regression): Between 1 and 4 years of age, the child loses purposeful hand skills and spoken language. Repetitive hand movements, such as hand wringing, clapping, or tapping, often develop during this stage.

Stage three (plateau): This stage can last for years. The regression slows. Seizures may become more frequent, and motor problems like rigidity or tremors can appear. Some communication and hand use may partially return.

Stage four (late motor deterioration): This stage typically begins after age 10. Muscle weakness, joint contractures, and scoliosis become prominent. The person may lose the ability to walk. Cognitive function, communication, and hand use generally remain stable through this stage.

How Is Rett Syndrome Diagnosed?

Diagnosis is primarily clinical, based on the presence of specific criteria established by international consensus. A doctor looks for a period of normal development followed by a loss of skills, the presence of repetitive hand movements, and the loss of spoken language.

A genetic test can confirm the diagnosis. This involves a blood test that looks for mutations in the MECP2 gene. The test identifies a mutation in about 95% to 97% of people who meet the clinical criteria for classic Rett syndrome. In some cases, a negative genetic test does not rule out the condition, and a clinical diagnosis may still be made based on symptoms.

Is There a Cure or Treatment for Rett Syndrome?

There is no cure for Rett syndrome. Treatment focuses on managing symptoms, improving quality of life, and supporting the individual’s specific needs. This is a lifelong condition that requires a coordinated approach.

Treatment commonly includes physical therapy to maintain mobility and prevent joint tightening, occupational therapy to support daily living skills, and speech therapy to aid communication. Medications may be used to manage specific symptoms such as seizures, breathing irregularities, or sleep disturbances. Regular monitoring for scoliosis, gastrointestinal issues, and nutritional status is also essential.

Research into targeted therapies is active. Some clinical trials are exploring treatments that aim to reactivate the normal copy of the MECP2 gene or address the downstream effects of the mutation. As of now, these remain experimental, and no gene therapy has been approved for Rett syndrome.

What Is the Life Expectancy for Someone With Rett Syndrome?

Many individuals with Rett syndrome live into adulthood and middle age. Because the condition is rare and survival data are limited, precise statistics are difficult to establish. However, with good medical care, particularly management of seizures, breathing issues, and scoliosis, many people with Rett syndrome live into their 40s or 50s.

The risk of sudden, unexplained death is higher in this population compared to the general population. Heart rhythm abnormalities and seizures are the most common causes of sudden death, which is why regular cardiac monitoring is often recommended.